Ministers have begun talks at the UN climate summit in Cancun, Mexico, amid warnings that time is running out to curb climate change. Top UN climate official Christiana Figueres said the fate of low-lying islands should be a “wake-up call”.Big differences remain between nations on issues such as cutting emissions, protection from climate impacts and inspections of others' emission curbs. It is unclear whether those issues can be resolved in the three days left.Mexican President Felipe Calderon congratulated negotiators for their work so far.Earlier, the UN Environment Programme formally presented delegates with the results of a study published two weeks ago. It showed that pledges on the table for curbing emissions will not be enough to keep the global average temperature rise below the levels that most governments say they want. The vast majority of countries want to keep the rise since pre-industrial times to within either 1.5C or 2C.